The present invention relates to a brazeable aluminum material, and more particularly to a corrosion resistant brazeable aluminum material for use to construct a heat exchanger or the like apparatuses which are manufactured by the brazing technique and must be resistant, and also relates to a method of producing the corrosion resistant aluminum material.
The term `aluminum` used herein is meant to include aluminum alloys.
The `thermal spraying` method is well known and has been proposed to form on aluminum a brazing agent layer composed of an Al-Si alloy, so as to make brazeable materials. Such a simple forming of the brazing agent layer is however not effective to render the materials resistant to corrosion.
It has also been proposed to melt spray Zn or its alloy onto the aluminum surface prior to the melt spraying of the brazing agent, with Zn or its alloy forming a corrosion resistant layer on the surface (see for example the Japanese Unexamined Patent Publication Nos. Hei. 1-157794 and Hel. 2-46969).
It is a disadvantage inherent in this idea that two sets of thermal spraying apparatuses have to be installed in and along a production line, one of them disposed upstream of the other, thus prolonging the production line and raising manufacture cost.
Further, since an entire surface of the brazing agent layer formed on the corrosion resistant layer is left in contact with ambient air, a stable oxide membrane is likely to be formed on the surface. Due to the fact that such a strong oxide membrane impairs the brazeability, any aluminum material producible by the two-step thermal spraying has not been put into commercial use. A first object of the present invention is therefore to provide a corrosion-resistant and brazeable aluminum material which has a thermally sprayed surface layer capable of being manufactured in a production line not prolonged, and nevertheless being highly brazeable.
A second object of the present invention is to provide a method of producing the aluminum material as set forth just above.
In order to achieve the first object, an aluminum material has a surface coated with a thermally sprayed layer which is composed of a homogenized mixture of a brazing metal and Zn (i.e., zinc ) or its alloy. The second object is achieved herein by blending a first powder of a brazing metal with a second powder of a corrosion resistant substance so as to prepare a powder mixture, and then thermally spraying this powder mixture onto an aluminum material surface.
Other objects, features and advantages of the present invention will become clear from the description made below referring to the drawings.